Settlement Engine Internals
Settlement Engine Internals - Technical Deep Dive
This document provides a detailed technical overview of the settlement engine that handles multi-chain transaction settlement in the Roru Protocol.
Architecture
Engine Components
Core Components:
Transaction Validator: Validates transactions before settlement
State Manager: Manages shielded state updates
Adapter Router: Routes to chain-specific adapters
Settlement Queue: Manages pending settlements
Confirmation Monitor: Tracks blockchain confirmations
Engine Structure
┌─────────────────────────────────────┐
│ Settlement Engine │
├─────────────────────────────────────┤
│ ┌──────────────┐ ┌──────────────┐ │
│ │ Validator │ │ State Manager│ │
│ └──────┬───────┘ └──────┬───────┘ │
│ │ │ │
│ ┌──────▼──────────────────▼───────┐ │
│ │ Adapter Router │ │
│ └──────┬──────────────────┬───────┘ │
│ │ │ │
│ ┌──────▼──────┐ ┌────────▼───────┐ │
│ │ Queue │ │ Confirmation │ │
│ │ Manager │ │ Monitor │ │
│ └─────────────┘ └────────────────┘ │
└─────────────────────────────────────┘Transaction Validation
Validation Process
Validation Steps:
Verify proof validity
Check nullifiers
Validate balance
Verify signatures
Check constraints
Validation Code:
fn validate_transaction(
tx: &Transaction,
state: &ShieldedState,
) -> Result<()> {
// Verify proof
verify_proof(&tx.proof, &state)?;
// Check nullifiers
for nullifier in &tx.nullifiers {
if state.nullifier_set.contains(nullifier) {
return Err(Error::DoubleSpend);
}
}
// Validate balance
verify_balance(&tx)?;
// Verify signatures
verify_signatures(&tx)?;
// Check constraints
verify_constraints(&tx)?;
Ok(())
}State Management
State Updates
Update Process:
Add new notes to tree
Add nullifiers to set
Update state root
Publish update
Update Code:
fn update_state(
state: &mut ShieldedState,
tx: &Transaction,
) -> Result<StateRoot> {
// Add new notes
for output in &tx.outputs {
let note = decrypt_note(&output.encrypted_note)?;
state.tree.insert_commitment(note.commitment())?;
}
// Add nullifiers
for nullifier in &tx.nullifiers {
state.nullifier_set.insert(nullifier.clone());
}
// Update root
let new_root = state.tree.update_root();
state.current_root = new_root;
Ok(new_root)
}Adapter Routing
Router Logic
Routing Process:
Determine target chains
Select appropriate adapters
Create settlement transactions
Route to adapters
Routing Code:
fn route_settlement(
tx: &Transaction,
adapters: &[ChainAdapter],
) -> Result<Vec<SettlementTx>> {
let mut settlements = Vec::new();
// Determine chains involved
let chains = determine_chains(tx)?;
for chain_id in chains {
let adapter = find_adapter(adapters, chain_id)?;
let settlement = adapter.create_settlement(tx)?;
settlements.push(settlement);
}
Ok(settlements)
}Settlement Queue
Queue Structure
Queue Format:
pub struct SettlementQueue {
pub pending: VecDeque<PendingSettlement>,
pub processing: HashMap<TxId, SettlementStatus>,
pub completed: Vec<CompletedSettlement>,
}Queue Operations
Enqueue:
fn enqueue_settlement(
queue: &mut SettlementQueue,
tx: &Transaction,
) -> Result<TxId> {
let tx_id = generate_tx_id(tx);
let pending = PendingSettlement {
tx_id,
transaction: tx.clone(),
timestamp: current_timestamp(),
retries: 0,
};
queue.pending.push_back(pending);
Ok(tx_id)
}Process:
async fn process_settlement(
queue: &mut SettlementQueue,
adapters: &[ChainAdapter],
) -> Result<()> {
if let Some(pending) = queue.pending.pop_front() {
queue.processing.insert(pending.tx_id, SettlementStatus::Processing);
match settle_transaction(&pending.transaction, adapters).await {
Ok(result) => {
queue.processing.remove(&pending.tx_id);
queue.completed.push(CompletedSettlement {
tx_id: pending.tx_id,
result,
});
}
Err(e) => {
handle_settlement_error(queue, pending, e)?;
}
}
}
Ok(())
}Confirmation Monitoring
Monitor Process
Monitoring Steps:
Submit settlement transactions
Track transaction hashes
Monitor confirmations
Update status
Finalize when confirmed
Monitor Code:
async fn monitor_confirmations(
monitor: &mut ConfirmationMonitor,
adapters: &[ChainAdapter],
) -> Result<()> {
for (tx_id, status) in &monitor.pending {
if let Some(adapter) = find_adapter_for_tx(adapters, tx_id) {
match adapter.get_confirmation(tx_id).await? {
ConfirmationStatus::Confirmed(block) => {
monitor.update_status(tx_id, ConfirmationStatus::Confirmed(block))?;
}
ConfirmationStatus::Pending => {
// Continue monitoring
}
ConfirmationStatus::Failed => {
monitor.update_status(tx_id, ConfirmationStatus::Failed)?;
}
}
}
}
Ok(())
}Multi-Chain Settlement
Atomic Settlement
Atomic Process:
Validate transaction
Create settlements for all chains
Submit all simultaneously
Monitor all confirmations
Finalize when all confirmed
Atomic Code:
async fn atomic_settlement(
tx: &Transaction,
adapters: &[ChainAdapter],
) -> Result<Vec<SettlementResult>> {
// Create all settlements
let settlements = create_settlements(tx, adapters)?;
// Submit all
let mut results = Vec::new();
for settlement in settlements {
let result = submit_settlement(&settlement).await?;
results.push(result);
}
// Monitor all
wait_for_all_confirmations(&results).await?;
Ok(results)
}Error Handling
Error Types
Settlement Errors:
Validation failure
Adapter errors
Network errors
Confirmation failures
State inconsistencies
Error Recovery
Recovery Strategies:
Retry with backoff
Fallback adapters
State rollback
Error reporting
Recovery Code:
fn handle_settlement_error(
queue: &mut SettlementQueue,
pending: PendingSettlement,
error: Error,
) -> Result<()> {
if pending.retries < MAX_RETRIES {
pending.retries += 1;
queue.pending.push_back(pending);
} else {
// Move to failed
queue.failed.push(FailedSettlement {
tx_id: pending.tx_id,
error,
});
}
Ok(())
}Performance
Optimization
Optimizations:
Batch settlements
Parallel processing
Efficient state updates
Caching
Metrics
Performance Metrics:
Settlement latency
Throughput
Confirmation time
Error rate
Security
Security Properties
Security Guarantees:
Atomic operations
State consistency
No double-spending
Cryptographic security
Threat Model
Protected Against:
Settlement attacks
State tampering
Double-spending
Network attacks
Conclusion
The settlement engine provides:
Reliability: Robust settlement
Efficiency: Optimized operations
Security: Cryptographic guarantees
Flexibility: Multi-chain support
Performance: High throughput
Understanding the engine is essential for settlement development.
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